Additional Nucleon Current Contributions to Neutrinoless Double Beta Decay

TL;DR

This paper investigates how momentum-dependent nucleon currents influence neutrinoless double beta decay, finding significant reductions in matrix elements and setting new limits on neutrino properties based on experimental data.

Contribution

It provides the first detailed calculation of nucleon current effects across multiple nuclei within the pn-RQRPA model, highlighting their impact on decay matrix elements.

Findings

Nucleon current effects reduce light neutrino matrix elements by about 30%.

Corrections vary by nucleus but exceed 25% in all cases.

Heavy neutrino effects are amplified, increasing matrix elements by a factor of 3.

Abstract

We have examined the importance of momentum dependent induced nucleon currents such as weak-magnetism and pseudoscalar couplings to the amplitude of neutrinoless double beta decay in the mechanisms of light and heavy Majorana neutrino as well as in that of Majoron emission. Such effects are expected to occur in all nuclear models in the direction of reducing the light neutrino matrix elements by about 30%. To test this we have performed a calculation of the nuclear matrix elements of the experimentally interesting nuclei A = 76, 82, 96, 100, 116, 128, 130, 136 and 150 within the pn-RQRPA. We have found that indeed such corrections vary somewhat from nucleus to nucleus, but in all cases they are greater than 25 percent. In the case of heavy neutrino the effect is much larger (a factor of 3). Combining out results with the best presently available experimental limits on the half-life of the neutrinoless double beta decay we have extracted new limits on the effective neutrino mass (light and heavy) and the effective Majoron coupling constant.